1. Field of the Invention
The present invention relates to compounds having a quite high antimicrobial activity and an excellent pharmacokinetics.
2. Prior Art
Intensive investigations have been done heretofore on antimicrobial compounds. Various pyridonecarboxylic acid derivatives are set forth as antimicrobial compounds in the Claims in the specifications of Japanese Patent Public Disclosure (KOKAI) Nos. 67269/1984 (U.S. Ser. No. 416406) and 214773/1985 (U.S. Ser. No. 581157). It is disclosed therein that compounds of the general formula: ##STR2## wherein X' represents N, CH or C--F, Y' represents a fluorine and R.sup.11 represents an ethyl, 2-fluoroethyl or cyclopropyl are preferred. However, compounds of the above general formula in which the basic substituent Z' which exerts a great influenece on the antimicrobial and physicochemical properties represents a pyrrolidine group disclosed heretofore are only those having a group of the formula: ##STR3## as shown in Example 11 in the specification of J.P. No. 67279/1984 (code No. of the compound: CI-934) and Examples 43 to 47 in the specification of J.P. No. 214773/1985.
However, the actual effect of antimicrobial agents is greatly influenced not only by the antimicrobial activity of the agent, but also by the pharmacokinetics of the agent. In other words, as excellent antimicrobial agent, it is most preferable to use compounds having both strong antimicrobial activity and good pharmacokinetics. It is well-known that the behavior in the human body, i.e., absorbability through the intestinal tract and stability for metabolic disposition depend on physicochemical properties of the compound, in particular, on solubility in water. Namely, if the water-solubility of the compound is extremely low, for example not more than 100 .mu.g/ml, the solubility speed of the compound in the intestinal tract becomes rate-determining, so that the absorption is bad and the compound is easily metabolized when it is absorbed through the intestinal tract.
From thus viewpoint, compound CI-934 has good water-solubility and strong antimicrobial activity against Gram-positive microorganisms, but has a drawback in that its activity against Gram-negative microorganisms is a little weak. On the other hand, the compounds described in examples 44 and 46 of the above J.P. 214773/1985, in which ethyl located on N-1 position of quinoline skeleton is changed to cyclopropyl, have strong antimicrobial activity against Gram-negative microorganisms, but from the extremely low water-solubility thereof it can be assumed that the pharmacokinetics thereof is bad.